/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.pop3;

/**
 * POP3Command stores POP3 command code constants.
 */

public final class POP3Command {
    /** Send user name. */
    public static final int USER = 0;
    /** Send password. */
    public static final int PASS = 1;
    /** Quit session. */
    public static final int QUIT = 2;
    /** Gets status. */
    public static final int STAT = 3;
    /** List message(s). */
    public static final int LIST = 4;
    /** Retrieve message(s). */
    public static final int RETR = 5;
    /** Delete message(s). */
    public static final int DELE = 6;
    /** No operation. Used as a session keepalive. */
    public static final int NOOP = 7;
    /** Reset session. */
    public static final int RSET = 8;
    /** Authorization. */
    public static final int APOP = 9;
    /** Retrieve top number lines from message. */
    public static final int TOP = 10;
    /** List unique message identifier(s). */
    public static final int UIDL = 11;
    /**
     * The capabilities command.
     *
     * @since 3.0
     */
    public static final int CAPA = 12;
    /**
     * Authentication
     *
     * @since 3.0
     */
    public static final int AUTH = 13;

    private static final int NEXT = AUTH + 1; // update as necessary when adding new entries

    static final String[] commands = { "USER", "PASS", "QUIT", "STAT", "LIST", "RETR", "DELE", "NOOP", "RSET", "APOP", "TOP", "UIDL", "CAPA", "AUTH", };

    static {
        if (commands.length != NEXT) {
            throw new IllegalStateException("Error in array definition");
        }
    }

    /**
     * Gets the POP3 protocol string command corresponding to a command code.
     *
     * @param command the command code
     * @return The POP3 protocol string command corresponding to a command code.
     */
    public static String getCommand(final int command) {
        return commands[command];
    }

    /** Cannot be instantiated. */
    private POP3Command() {
    }
}
